1. Field of the Invention
The present invention relates to a machine-translation apparatus and a machine-translation method for translating a sentence in a source language that has been input into a sentence in a target language.
2. Description of the Related Art
As natural language processing technology advances, machine-translation apparatuses that receive an input of a source-language sentence expressed in a source language, convert the input sentence into a sentence in a desired target language, and output the result of the conversion have been developed. For example, a machine-translation apparatus that translates a text or the like expressed in Japanese into another language such as English or Chinese has been in practical use. To translate the input sentence in the source language more faithfully with a higher level of precision, such a machine-translation apparatus needs to include a mechanism that is able to find a sufficient solution for the diversity and the ambiguity of natural languages.
For example, JP-A 2000-10974 (KOKAI) proposes a technique by which a case element that is missing in a sentence in a source language is supplementarily provided through an interaction with the user. This technique realizes a translating apparatus that offers a solution for the ambiguity that arises during the interpretation of the source language sentence and achieves a high level of precision without making analysis errors.
However, there are some situations in which, even if a source language sentence has no analytical ambiguity, the translating apparatus is not able to generate a translated sentence that sufficiently reflects the implied intention of the source language sentence. For example, any source language has certain words or phrases that are usually omitted due to a cultural background, the diction, or the pragmatics. It is often the case that omitting such words or phrases causes no grammatical problem in the source language. Thus, it is difficult to detect the situation in which, when a source language sentence that involves omission of such words or phrases has been translated, the translated sentence does not properly reflect the implied intention of the source language sentence.
In addition, generally speaking, users of machine-translation apparatuses do not usually have sufficient knowledge of the target language. Thus, it is extremely difficult for the users to check the translated sentence that has been output by the apparatus so as to determine that the translated sentence does not properly reflect the user's intention and to further input a source language sentence again with supplementary information for obtaining a more appropriate translated sentence.